The present invention relates to subsurface pressure injection into soil of chemicals such as herbicides, insecticides, nematocides, fertilizers, fungicides and other materials requiring soil incorporation.
In one class of subsurface application of chemicals, dispensers are moved underground while chemicals are spread by the dispensers.
In one type of prior art applicator of this class, tractor-drawn injector applicators penetrate the soil and inject chemicals at several spaced locations at one depth behind the tractor. Another type of prior art applicator of this class includes a dispenser attached to an implement such as a spade or a plow to introduce chemicals into a trench formed by the implement as it is pulled through the ground behind a tractor. These two types of applicators have the disadvantages of: (1) not producing uniform distribution of chemicals throughout the soil; (2) breaking a substantial portion of the soil surface; and (3) being only locally effective.
A third type of prior art technique of this class is to first apply the chemicals to the surface of the soil and subsequently mix the chemicals with the soil by tilling the soil in some fashion. This technique has the disadvantages of: (1) causing variable amounts of the chemical to be lost or wasted in the uppermost, relatively dry layers; (2) mixing the plant residue into the uppermost layers of soil and loosening the soil, thus causing the soil surface to become susceptible to erosion due to water runoff or wind; and (3) requiring the application of chemicals and their mixing to be done in two separate operations in most instances.
In still another type of prior art technique of this class, a horizontally disposed implement, or sweep, to which a plurality of horizontally oriented spray nozzles are secured is connected directly to a tractor or to a tractor-drawn frame and drawn beneath the surface of the soil and, upon pumping chemicals such as herbicides or fertilizers through the nozzles, a layer of chemicals is introduced into the soil. This technique has the disadvantage of providing insufficient distribution of the chemicals into the soil because the chemicals are applied in a discrete layer rather than being uniformly mixed into the upper soil zone where most weed seeds germinate.